Generally, a vacuum pump with a rotor that rotates at high speeds, such as a turbomolecular pump, is provided with a protective net at an inlet area in order to prevent foreign matter from entering the pump. A generally used method for attaching the protective net at the inlet area includes a method for placing a protective net on the inlet flange and attaching a C-shaped ring for fixation of the protective net to the flange (see, for example, Cited Document 1).
Patent Document 1: Japanese Patent Laid-open Publication No. Hei-11-247790 (FIG. 4)